1. Field of the Invention
The present invention relates to a grasping forceps insertable into a channel formed in an endoscope for allowing a treating instrument to pass therethrough. The forceps is used for grasping and picking out an object such as a foreign body, polypus and so on within a body cavity.
2. Description of the Related Art
Recently, in addition to the medical examination of a body cavity by an endoscope, there has been well-known in the art a grasping forceps for an endoscope such as an in vivo inspection forceps, where the grasping forceps is inserted into a treating instrument passing channel formed in the endoscope. The forceps is inserted into the body cavity for the purpose of grasping and recovering a foreign body within a living body or for grasping and picking out cellular tissue to be inspected.
The grasping forceps for the endoscope comprises a flexible insertion section composed of a coil sheath and the like externally covered with, for example, a flexible resin tube, an operation wire passing through this insertion section, an operating section connected with the operating wire at its hand-side end, and a grasping section composed of a plurality of elastic grasping members arranged at the leading end of the operating wire.
For example, as shown in FIG. 1, the elastic grasping section 2 of the grasping forceps 1 for the endoscope comprises three elastic grasping members 2a, 2b, 2c. This elastic grasping section 2 is connected at its hand-side end with the operating wire (not illustrated) passing through the interior of the insertion section 3, and the elastic grasping members 2a, 2b, 2c are projected and concealed from the leading end face 3a of the insertion section 3 in accordance with the advancing and retreating operations of the operating wire so as to open and close the elastic grasping section 2.
That is, when the operating wire is operationally pushed out, the elastic grasping members 2a, 2b, 2c are projected from the leading end face 3a of the insertion section 3. Thereupon, circular pawls 4a, 4b, 4c formed at the leading end portions of the respective elastic grasping members 2a, 2b, 2c are spread outward from the center of the insertion section 3 due to the elastic restoring forces of the elastic grasping members 2a, 2b, 2c. On one hand, as the elastic grasping members 2a, 2b, 2c are pulled into the insertion section 3 by the traction operation of the operating wire, the circular pawls 4a, 4b, 4c formed at the leading end portions of the elastic grasping members 2a, 2b, 2c are closed gradually to grasp a foreign body and the like.
But, since this forceps 1 for the endoscope has the elastic grasping section 2 composed of three grasping members 2a, 2b, 2c, the gaps between the adjacent elastic grasping members are wide. Therefore, the once grasped living body tissue or foreign body might occasionally drop through the gaps between the elastic grasping members.
Thereupon, in order to prevent the once grasped living body tissue or foreign body from dropping through the gaps between the elastic grasping members, the applicant of the present invention has proposed a forceps for an endoscope in Japanese Patent Application No. Hei. 6 (1994)-181503, wherein the elastic grasping section of the forceps for the endoscope comprises at least four elastic grasping members of different lengths, the circular pawls formed at the leading end portions of the elastic grasping members are arranged so as to come into a spiral fashion to narrow the gaps between the elastic grasping members when the elastic grasping members comprising those elastic grasping members of different lengths are spread, and the circular pawls formed at the leading end portions of the elastic grasping members can be converged within the insertion section in a longitudinally aligned manner.
In the forceps for the endoscope proposed in the above-mentioned Japanese Patent Application No. Hei. 6 (1994)-181503, however, when the elastic grasping portion composed of the elastic grasping members of different lengths is spread, since the elastic grasping section is constructed such that the circular pawls formed at the leading end portions of the elastic grasping members can be arranged in the spiral fashion, the longest elastic grasping member and the shortest grasping member are located at positions adjacent each other in the opened state.
As shown in FIG. 2, when the longest elastic grasping member 5e and the shortest elastic grasping member 5a of the elastic grasping members 5a, 5b, 5c, 5d, 5e having different lengths forming the elastic grasping section 5 are located at adjacent positions at random, the positional differential distance "a" between the circular grasping portion 6e of the longest elastic grasping member 5e and the circular grasping portion 6a of the shortest elastic grasping member 5a in the longitudinal direction of the insertion section becomes maximum in the opened state of the elastic grasping section 5, so that it is unlikely that they grasp a small polypus or foreign body.